Classes

Question 1

Introduction to Classes

Answer 1

Classes are a tool that developers use to quickly produce similar objects.

Question 2

Class example with constructor & call new class instance

Answer 2

class Dog {
  constructor(name) {
    this._name = name;
    this._behavior = 0;
  }

  get name() {
    return this._name;
  }

  get behavior() {
    return this._behavior;
  }   

incrementBehavior() {
this._behavior++;
}
}

const halley = new Dog(‘Halley’);

Question 3

What must call on the first line of subclass constructors?

Answer 3

super(name);

example:
class Cat extends Animal {
  constructor(name, usesLitter) {
    super(name);
    this._usesLitter = usesLitter;
  }
}

Question 4

Review: Classes

Answer 4

Classes are templates for objects.
Javascript calls a constructor method when we create a new instance of a class.
Inheritance is when we create a parent class with properties and methods that we can extend to child classes.
We use the extends keyword to create a subclass.
The super keyword calls the constructor() of a parent class.
Static methods are called on the class, but not on instances of the class.

Question 5

Example:
Parent & Child class:
class Nurse extends HospitalEmployee {}

Answer 5

class HospitalEmployee {
  constructor(name) {
    this._name = name;
    this._remainingVacationDays = 20;
  }

  get name() {
    return this._name;
  }

  get remainingVacationDays() {
    return this._remainingVacationDays;
  }

takeVacationDays(daysOff) {
this._remainingVacationDays -= daysOff;
}

  static generatePassword() {
    return Math.floor(Math.random() * 10000);
  }
}

class Nurse extends HospitalEmployee {
  constructor(name, certifications) {
    super(name);
    this._certifications = certifications;
  } 

  get certifications() {
    return this._certifications;
  }

addCertification(newCertification) {
this.certifications.push(newCertification);
}
}

const nurseOlynyk = new Nurse(‘Olynyk’, [‘Trauma’,’Pediatrics’]);
nurseOlynyk.takeVacationDays(5);
console.log(nurseOlynyk.remainingVacationDays);
nurseOlynyk.addCertification(‘Genetics’);
console.log(nurseOlynyk.certifications);